Do you think that you could enter paradise unless God takes cognizance of your having striven hard [in His cause], and takes cognizance of your having been patient in adversity?
Al-Imran (The Family of Imran) Verse 142
I heard Allah's Apostle saying, "The rights of a Muslim on the Muslims are to follow the funeral processions, to accept invitation and to reply the sneezer
Sahih Bukhari: Volume 2, Book 23, Number 332